Haylie Duff

A sister's wedding is a big day for anyone – and it's no different for Haylie Duff, who watched proudly as little sister Hilarygot married on Saturday.

Reflecting on the nuptials on Monday, Haylie, 25, wrote on Twitter: "what a special weekend filled with love and beautiful memories." (The post later disappeared, but not before being reposted by a number of Haylie's fans.)

Hilary, 22, exchanged vows with Canadian hockey player Mike Comrie, 29, in Santa Barbara, Calif., on Saturday. "Mike held his arm around Hilary for most of the romantic, candlelit ceremony, and they both looked extremely happy," an eyewitness told PEOPLE.

 Hilary Duff, sharing a sisters' night out with older sib Haylie at Teddy's inside the Hollywood Roosevelt Hotel. The starlet and her sister – plus several friends – made an energetic arrival, and stayed revved up all night: Hilary danced provocatively to Britney Spears's new single, "Womanizer," and offered her girlfriends little lapdances, an onlooker tells us. And the sisters were in for the long haul, talking and dancing until the club closed. Also there: Frankie Delgado and Doug Reinhart.

 Hilary Duff, sharing a sisters' night out with older sib Haylie at Teddy's inside the Hollywood Roosevelt Hotel. The starlet and her sister – plus several friends – made an energetic arrival, and stayed revved up all night: Hilary danced provocatively to Britney Spears's new single, "Womanizer," and offered her girlfriends little lapdances, an onlooker tells us. And the sisters were in for the long haul, talking and dancing until the club closed. Also there: Frankie Delgado and Doug Reinhart.

How does Hilary Duff keep conversation hot with her hockey-star boyfriend Mike Comrie? Older sister Haylie Duff spilled the beans to PEOPLE Tuesday.

"I actually caught her with a copy of the Hockey for Dummies book," Duff, 22, said at the opening of the Foley+Corinna store in West Hollywood. Big sis says she "adores" Comrie – and says it's actually distance that makes things work between him and 20-year-old Hilary. "He lives in New York and
she lives here, and they really put in a big effort to see each other."– Shayna Arnold

 New couple alert? Haylie Duff, partying with beau Brody Jenner and some friends (including Hilary Duff) at West Hollywood's Hyde. The pair sat side-by-side, laughing and appearing to have a wonderful time. Soon, they split from the younger Duff and ventured outside to the patio where, an onlooker tells us, the two whispered into each other's ears. A source says they're close friends, but according to an onlooker, the pair was inseparable.

Paris and Nicky they're not, but Hilary and Haylie Duff will get to unleash their inner Hiltons as they start filming the new movie Material Girls, about two party-loving heiresses who lose their family fortune. The sisters, who collaborated last year on the song "Our Lips Are Sealed" (for Hilary's A Cinderella Story soundtrack) and hit the road together, recently chatted with PEOPLE about sharing the spotlight, crushing on Johnny Depp and dealing with overzealous fans.

Jessica and Ashlee, Britney and Jamie-Lynn – Hollywood's fascination with sisters is alive and well, and the Duff family is taking it up a notch. Actress-singer Hilary and big sis Haylie – who teamed up for a remake of the 1981 Go-Go's hit song "Our Lips Are Sealed" and toured together over the summer – are taking on the movie Material Girls, set to begin filming in April. "It’s just a fun movie about sisters who have a ton of money," Haylie told us recently. "They’re heiresses in the movie, with all their money. Then it’s kind of how they turn into good people. It’s cool. It’s a funny movie, and we’re remaking the song by Madonna." As for what else she's up to, the elder Duff says, "I'm working on Joan of Arcadia right now. I'm doing five weeks over there. I'm having so much fun. Amber Tamblyn is wonderful." Any word on Hilary? "My sister’s finally finishing up the Most Wanted tour that we did together in the U.S. She's doing another leg of it in Canada right now," says Haylie. "So she gets back in a couple of weeks. Then we're doing a Material Girls tour to promote the movie. We'll do that together next summer, June maybe." Stay tuned ...